1. Field of the Invention
The present invention generally relates to locking devices and more particularly to an improvement in an electromagnetic door lock device.
2. Prior Art
Various types of electromagnetic door lock devices have been devised and utilized. Most are cumbersome, expensive, difficult to install and adjust and subject to damage. See, for example, U.S. Pat. No. 4,487,437, which discloses a device which operates under shear and employs a specially-configured electromagnet housing which can easily be damaged, as can the electromagnet inside the housing, if the door lock components are not precisely aligned. Any misalignment also causes the lock to malfunction, bind, jam, etc. Such a lock has limited applications.
The door lock of U.S. Pat. No. 4,826,223 solves such problems by placing a separate tab plate on one or both opposite ends of the housing so that only the tab plate is subject to stress by the movable armature of the lock. However, it would be desirable to further improve the ease with which a device such as that of U.S. Pat. No. 4,826,223 can be installed, aligned and adjusted for ideal functioning. In some cases, as when the armature and electromagnet are not in proper alignment, the tab of the tab plate of the aforesaid patent has had a tendency to bind against the armature when the electromagnet is energized, delaying opening of the door when the electromagnet is deenergized. It would be desirable to eliminate this delay, while facilitating easy visual alignment of the door lock components. Such an improvement to provide these advantages should be adjustable, simple, efficient and durable.